Fault code 0122: Diagnosis/troubleshooting

NOTE: Visual inspection: In the next troubleshooting section, please check first that the affected pins on the rear left door control module plug connection are neither damaged nor corroded. The wiring and plugs of the affected components must also be checked for external damage and correct contacts. Repair damaged or corroded pins if possible, otherwise replace affected pins. Repair or replace damaged wires.

NOTE: Sporadic faults: In the event of faults that occur sporadically, the wiring positions that are linked to moving parts on and in the vehicle must be checked for each system. Various statuses that can cause faults must be simulated with the help of the wiring diagram.

NOTE: Battery voltage: A battery voltage of between 11.4 and 14.5 V is required for the following troubleshooting procedure. This must be checked and provided, if necessary. On the vehicle electrical system, the voltage to the fuse (input side) must be guaranteed.

NOTE: The door warning light and the door exit light are activated together on opening and closing the door. The voltage supply, however, is split on two separate pins.

WORK INSTRUCTION CHART

Work instruction			Display OK	If not OK
1	Check bulbs of rear left door warning and exit lights	Check resistance of bulb filaments.	< 5 Ω Step 2	Replace bulb. → End
2	Check rear left door warning and exit lights	Switch off ignition. Pull off plug on door warning light. Measure resistance between contact springs on bulb holder and the associated pin.	< 5 Ω Go to step 3	Replace door warning light. → End
2	Check rear left door warning and exit lights	Pull off plug on door exit light. Measure resistance between contact springs on bulb holder and the associated pin.	< 5 Ω Go to step 3	Replace door exit light. → End
3	Check wiring for short circuit to B+	Pull off plug B on rear left door control module. Switch on ignition. Measure voltage between control module plug B, pin 9 (door exit light) and ground.	< 0.3 V Go to step 4	Repair wiring. → End
		Measure voltage between control module plug B, pin 1 (door warning light) and ground.
		Measure voltage between control module plug A, pin 8 and ground.
4	Check wiring for short circuit to ground	Measure resistance between control module plug B, pin 9 (door exit light) and ground.	∞ Ω Go to step 5	Repair wiring. → End
		Measure resistance between control module plug B, pin 1 (door warning light) and ground.
		Measure resistance between control module plug B, pin 8 and ground.
5	Check for short circuit between wires	Remove bulbs. Measure resistance between control module plug B, pins 1 and 8.	∞ Ω Go to step 6	Repair wiring. → End
		Measure resistance between control module plug B, pins 9 and 8.
		Measure resistance between control module plug B, pins 1 and 9.
6	Check wiring for open circuit	Measure resistance between control module plug B, pin 8 and door warning light plug, pin 1 as well as door exit light plug, pin 1.	< 5 Ω Go to step 7	Repair wiring. → End
		Measure resistance between control module plug B, pin 9 and door exit light plug, pin 2.
		Measure resistance between control module plug B, pin 1 and door warning light plug, pin 2.
7	Replace rear left door control module		→ End